Dismantling: Briggs & Stratton 10.8v Instart Battery | IS12B-593560

[Chant]

Rach and anyone else that can shed some light on this.  The instart battery that you dismantled has two small wires extending from the circuit board and attached with sealant to the cells.  My questions:  Is it on piece of two strand wire in a loop from the circuit board or two pieces of two strad wire and both are attached to the board?  Also, is the a temp sensor attached to the end or middle of the wires?  Can you tell me what that sensor is?  My son picked up a battery like this at a yard sale knowing I need one but unfortunately it was dismantled.  He knew I could rebuild the cells but the wires I'm speaking of were cut/torn off so I don't know if there's anything I can do without knowing what those wires do.  I'm sure they are a temp sensor but I can't see an actual sensor in your pictures.
Thanks to all for any help.
Take care,
Chant

[Mick]

Hi Chant, and welcome to TGMF.

It's definitely a temperature sensor but what type I haven't a clue.  I believe it stops the charging process should the batteries become over heated during charging.

If I get a chance I'll see if I can find any info on the sensor.     

[Chant]

Thanks a lot for your help!  I believe it's a thermistor but don't know much about them.
 I think there's a way to measure their reistance but again, I don't know how. If you have and boards or even just the sensor with wires attached I'm really interested. But knowing what the sensor is will work too!
Take care,
Chant

[computerix]

I recently received a Briggs and Stratton instart battery from my mother-in-law. The green and red LEDs on the charger were blinking alternately. The individual cells of the battery were charged differently and unfortunately the charger cannot compensate for this. I charged the cells individually to the same voltage and this solved the problem. I wrote an iFixit article about this. Maybe it will help someone with the same issue.
https://www.ifixit.com/Guide/Briggs+and+Stratton+instart+-+Battery+imbalance+repair/172196

[Mick]

computerix, welcome to TGMF.

Thank you for posting that info, I'm sure it will come in handy.  The batteries I had problems with were suffering with the flashing lights when charging, but not sure if the same as you described.  I posted a couple of them on Youtube you can see  them here,

https://youtube.com/shorts/Is13NuvhSJk?si=G3i8wcr-A1I_WVW-
https://youtube.com/shorts/IfMtuh2vIk8?si=iPXavnl-nfoAmNn2

[computerix]

Thank you for posting that info, I'm sure it will come in handy.  The batteries I had problems with were suffering with the flashing lights when charging, but not sure if the same as you described.

Thanks for the reply. I was aware that this is not the same problem. In your case I also think that one cell is completly dead and therefore only a replacement will help. I wanted to help those who think they need to replace the cells in any case.

[Mick]

Thanks, like I said I'm sure it will be handy info for those having the same issue as you mentioned.

I think I might have enough donor batteries to try and make a good one out of, but need to get or make up a spot welder to strap them together again.  Don't think my soldering iron will do it as the tip is too small.

[PDR]

Summary - you can recover these batteries when one or two cells go down. The process needs two paperclips, a basic digital volt meter and a programmable RC model battery charger (find a friend or buy one for about £25 - still cheaper than a new instart battery).

[if you're still reading - the story goes like this]

If anyone is interested - I had the same battery with precisely the same symptoms which was not only annoying but seriously inconvenient as my mower has no manual start chord and replacement batteries are simply unobtainable at the moment.

So I stripped the batter as in this thread, but didn't remove the cells from the circuit board. I checked to individual cells with a digital voltmeter and found that while the centre one was at a reasonable 3.98v the other two were down well below 1v, which isn't good for a lithium cell. My first thought was that these two cells were probably toast and should be replaced, but I couldn't find any of these in stock anywhere either (indeed I wonder if this is the cause of the shortage of new instart packs!). So I needed a plan C.

Now as it happens I have a hobby flying radio-controlled aeroplanes, and these use large lithium-polymer batteries so I'm fairly familiar with them and have sometimes had some success tickling them back into life. I ticked a couple of unbent paperclips under the welded tabs of one of the outer cells so that I could attach crocodile clips to them, and connected them to an RC model charger. Now the charger won't charge these cells as "lithium" cells because the voltage so low it triggers a fault. This is also why the Briggs & STratton charger refuses to charge them.

The "trick" is to just get some charge into the cell to get the voltage up to normal limits, so I set the chartger in NiMH (Nickel Metal-Hydride) mode and told the charger it was a 3 cell pack with a harge current of 1.5Amps. NiMH cells are charged at constant current so this squirts current into the cell regardless of the voltage. This is safe PROVIDED you don't exceed around 4.1 volts, so I monitoired the voltage and stopped when it was the same as the "good" middle cell (took about 30 minutes). I repeated the process with the other dead cell so that I now had all three cells at roughly the same voltage (3.95v). I then reassembled the battery pack and found that it would now charge normally on the briggs & stratton charger. Once fully charged I found it lasted for about 15 minutes of cranking on the mower (because the fuel filter was clogged, but that's another story!). It then recharged normally, so I regard it as fully recovered.

PDR

[Mick]

PDR, Hi and welcome to TGMF.

Interesting, I did wonder if that would work.  I've see people do similar to power tool battery packs by connecting a dead battery to a good one to to put some charge back in so the charger can see it.

Would connecting via your method, a good charged cell to one of those bad cells also work?

[PDR]

Probably not a good idea with lithium cells - it would risk damaging the "good" one

PDR